The focus of this proposal centers on the psychological processes and neural mechanisms underlying the representation of temporal information. The cerebellum has been found to be essential in tasks requiring the representation of short temporal intervals. The cerebellar timing hypothesis provides a parsimonious account of a number of disparate cerebellar functions, including its role in motor control, certain perceptual tasks, and sensorimotor learning. Such tasks involve event timing, situations in which explicit representations of the temporal events are required. In contrast, timing may be an emergent property in many actions, reflecting temporal consistencies that arise through the control of other movement parameters. Preliminary work suggests that the importance of the cerebellum is diminished under such conditions. The specific goals are fourfold: First, the proposed distinction between event timing and emergent timing will be examined in a series of movement tasks involving neurologically impaired and neurologically healthy individuals. Second, functional magnetic resonance imaging will be used to test the hypothesis that the cerebellum is critical for movements involving event timing. These experiments will evaluate whether the cerebellar involvement is related to the representation of a temporally defined goal, the control of transition events related to the initiation and termination of the actions, or a combination of these factors. Third, the performance of patients with cerebellar, basal ganglia, or frontal pathology will be compared on motor and perceptual temporal processing tasks. The experiments in this section are designed to isolate processes involved in temporal representation from those associated with the working memory and/or attentional demands required in such tasks. Fourth, functional neuroimaging will be used to directly examine neural regions recruited during motor and perceptual timing tasks, and to examine the relationship of event timing to the more general cognitive function of generating predictions about future events. The proposed studies will contribute to our understanding of how temporal information is processed in the brain, and provide important new insights into the contribution of the cerebellum to movement and cognition.